A quality attribute of Suzuki-Miyura coupling reactions is to measure residual levels of phosphine ligands in the reaction product. Residual phosphine ligands can be present in non-oxidized and oxidized forms. The non-oxidized and oxidized forms have different UV chromophores and can have differing solubility. These differences can preclude accurate and precise quantification. The extent of oxidation is difficult to prevent and control for calibration standards and test materials. This paper describes a method for derivatizing residual phosphines to the oxidized form. The oxidized form is stable and provides a basis for accurate quantification of residual phosphines. This overcomes the challenges for quantifying the non-oxidized and oxidized forms.
